Main Controlling Factors And Favorable Target Prediction Of Oil And Gas Accumulation In The Lower Shahejie Formation Of Beidagang Area

Beidagang area is located in the middle part of Qikou Sag,which is rich in oil and gas,especially the reservoir in the lower part of Shahejie formation.At present,how to tap the exploration and development potential of Shaxia sub section in Beidagang area has become a crucial issue.The successful solution of this subject will be of great significance to the exploration and development of oil and gas in Beidagang area and even Qikou depression in the future.Therefore,based on the existing regional geological data,geochemical data,seismic data,logging data,well logging data,testing data and oil testing data in the Beidagang area,this paper systematically analyzes the oil and gas accumulation conditions in five aspects: source rock conditions,reservoir conditions,caprock conditions,trap conditions and transportation conditions,and combines the oil and gas distribution characteristics of the lower Shaxia sub section to analyze the Beidagang area This paper studies the main controlling factors of oil and gas accumulation in the lower Shahejie formation,and further predicts the favorable targets of oil and gas accumulation,so as to provide theoretical basis for the next stage of oil and gas exploration and development in the lower Shahejie formation of Beidagang area.There are four aspects in this study:(1)The source rock conditions of the third member of Shahejie Formation in Beidagang area are good,and the effective source rock is widely distributed and thick.The lower Shahejie Formation in Beidagang area has good reservoir conditions and relatively developed sand body,which belongs to the medium porosity,ultra-low permeability and medium permeability reservoir.In Beidagang area,the mudstone caprock in the middle member of Shahejie formation is in good condition,with a wide range of distribution and a large thickness;the mudstone caprock is less damaged by faults and has a strong sealing ability of fault cap configuration.The main types of traps developed in the lower Shahejie sub member of Beidagang area are fault block trap,fault nose trap and anticline trap,which are mainly distributed in the middle and northwest.In Beidagang area,there are 25 dominant vertical channels of oil source fault and 5 lateral channels of sand body.(2)The main types of oil and gas reservoirs in the lower Shaxia sub member of Beidagang area are anticline type,fault nose type,fault block type,fault lithology composite type and updip pinch out type.The lower Shaxia sub member of the Beidagang area is rich in oil and gas,especially in the central part,and a small amount in the northwest.(3)The oil and gas accumulation in the lower Shaxia sub member of Beidagang area is mainly controlled by three factors: fault cap configuration,sand land ratio and dominant transport channel.Among them,fault cap configuration controls the oil and gas accumulation horizon,sand land ratio controls the oil and gas accumulation area,and dominant transport channel controls the oil and gas accumulation position.(4)There are 5 favorable targets for oil and gas accumulation predicted in the lower Shahejie formation of Beidagang area,with a total area of 13.23km2,mainly distributed in the northeast and a few in the south.